new feature: "ifconfig-ipv6-push" (from ccd/ config)

new feature: "ifconfig-ipv6-push" (from ccd/ config)
  affects options.h, options.c, multi.c
  benefit: static IPv6 address assignment from radiusplugin (etc)
rewritten get_ipv6_addr() to handle IPv6 addresses with and without "/bits"
  affects route.c and mainly options.c
  benefit: ifconfig-ipv6, ifconfig-ipv6-pool can now be accept
  configurations with networks != /64 (the rest of the implementation
  is not yet completely there, but this is imporant preparation work to
  be able to add /bits to "push 'ifconfig-ipv6 ...'" later on without
  breaking clients
do not try to add/delete IPv6 routes if no IPv6 on tunnel
  affects: route.c
  benefit: avoid error messages, and make IPv6 troubleshooting easier
flag as "config error" if --ifconfig-ipv6-pool used without --ifconfig-ipv6
flag as "config error" if --ifconfig-ipv6-pool used without --server
print warning if --ifconfig-ipv6 is used without --tun-ipv6
changes documented in more detail in ChangeLog.IPv6

* release patch set 20100114-1
(cherry picked from commit c04f774c7e9bed602818b1fe2ff4e83cf913d471)